Method for motion estimated and compensated field rate up-conversion (FRU) for video applications and device for actuating such method

Abstract

A method and a device for motion estimated and compensated Field Rate Up-conversion (FRU) for video applications is disclosed and claimed. The invention provides for dividing an image field to be interpolated into a plurality of image blocks, where each image block includes a respective set of image elements of the image field. In one embodiment, for each image block of a subset of image blocks, a group of neighboring image blocks is selected. A motion vector for the image block is estimated that describes the movement of the image block from a previous image field to a current image field on the basis of predictor motion vectors associated to the group of neighboring image blocks. Each image element of the image block is determined by interpolation of two corresponding image elements in the previous and current image fields related by the estimated motion vector. To estimate a motion vector, the invention provides for applying each of the predictor motion vectors to the image block to determine a respective pair of corresponding image blocks in the previous and current image fields. For each of the pairs of corresponding image blocks, an error function which is the Sum of luminance Absolute Difference (SAD) between corresponding image elements in the pair of corresponding image blocks is evaluated. For each pair of the predictor motion vectors, a degree of homogeneity is also evaluated, followed by the application of a fuzzy rule having an activation level that is proportional to the degree of homogeneity of the pair of predictor motion vectors and the error functions of the pair of predictor motion vectors. An optimum fuzzy rule having the highest activation level is selected, from which the best predictor motion vector is determined, having the smaller error function of the pair associated to the optimum fuzzy rule. In most cases, the motion vector for the image block is estimated on the basis of the best predictor motion vector.

Description

1. Field of the InventionThe present invention relates to a method for motion estimated and compensated Field Rate Up-conversion (FRU) for video applications, and to a device for actuating such method More particularly, the invention relates to a method based on a so-called "block-matching technique".2. Discussion of the Related ArtThe market introduction of high-end TV sets, based on 100 Hz Cathodic Ray Tubes (CRTs), required the development of reliable Field Rate Up-conversion (FRU) techniques to remove artifacts such as large area flicker and line flicker.Methods for FRU are known (hereafter referred to as "standard FRU methods") that add interpolated missing image fields to a video source. The standard methods interpolate the missing fields to be displayed on the CRT without performing an estimation and compensation of motion of moving objects in successive image fields of the video source.The standard FRU methods are satisfactory for improving the quality of an image and reduci...

AI Technical Summary

Problems solved by technology

However, when FRU is performed by means of the standard methods, new artifacts can appear in the displayed image.

In fact, the standard interpolation algorithms are not able to detect an objects' motion, and this can lead to interpolated fields in which the moving objects are displayed in wrong positions.

Such artifacts are visible to the viewer, inducing a blurring effect for fast moving objects and considerably reducing the quality of the displayed images.

However, this would require a large number of calculations and substantial memory.

This means that if the errors err[i] are too high and the vectors are not homogeneous, then the predictor motion vector with the minimum error value is directly chosen as candidate motion vector for block K(x,y), because the weighting of its components is not reliable.

Since the previously described field interpolation method is recursive, problems exist when, for a "next" source field (belonging to the next movie picture), motion is to be estimated; the information of motion estimated two fields previous has been "lost" due to the intervening zero motion vector.

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